1. Field of the Invention
The present invention relates to a pressurizing pump device for discharging a pressurizing fluid by repeating suction and delivery, a liquid ejection apparatus, a flow path structure of a pressurizing pump, a method of stopping driving a pressurizing pump and a method of releasing a pressurization of a pressurizing fluid.
2. Related Art
In a background art, various kinds of printing apparatus have been developed and according to a kind of a printing apparatus, for example, for office use or for business, a large amount of ink is consumed in accordance with an increase in a printing frequency and therefore, the printing apparatus needs to mount an ink cartridge having a large capacity. However, when a kind of a printing apparatus mounted with an ink cartridge on a carriage (on-carriage type) is simply mounted with an ink cartridge having a large capacity, the carriage and therefore, the printing apparatus is large-sized and also the carriage per se is applied with a large load. Therefore, there has been developed a printing apparatus of an off-carriage type constituting a carriage and an ink cartridge by the separate members.
According to a printing apparatus of an off-carriage type, ink at inside of an ink cartridge needs to deliver to a side of a carriage (subtank on carriage). Therefore, the printing apparatus is mounted with a pressurizing pump and an ink pack at inside of a carriage is pressed to crash by delivering air pressurized by a pressurizing pump to a space at inside of the ink cartridge to thereby press ink to a side of the carriage. Further, the pressurizing pump repeats discharge of delivering out pressurized air and suction of taking in atmosphere into the pressurizing pump after the discharge to thereby supply ink.
As the pressurizing pump, a diaphragm type pump shown in, for example, JP-A-2000-352379 (pages 4 through 7, FIG. 2) is known. The diaphragm type pump is a pump of delivering pressurizing air by converting rotational movement of a drive motor into vertical movement of a diaphragm and expanding and contracting a pump chamber in accordance therewith. The diaphragm type pump is provided with a plurality (three in the pump of JP-A-2000-352379) of pump chambers on the same plane and the pump chambers repeat expanding and contracting operation successively in accordance with rotation of the drive motor to successively deliver pressurizing air.
However, when a diaphragm type pump shown in JP-A-2000-352379 is used, a plurality of pump chambers are present on a plane orthogonal to an axis center of the pump and therefore, the pump is large-sized in a diameter direction to pose a problem that a pressurizing pump and therefore, a printing apparatus is large-sized. Particularly, although a printing apparatus is requested to be downsized, since with regard to a size of a printing apparatus, also a size of a pressurizing pump occupies a large weight, there is a request of intending to reduce the size of the pressurizing pump as less as possible.
Further, a check valve is arranged on a delivery path of a pressurizing pump to increase a pressurized amount at each time of repeating pressurizing operation. Therefore, after the pressurizing pump is operated to pressurize, a high pressure state is maintained in an air supply tube constituting a way of passing pressurizing air. Meanwhile, when inside of the air supply tube is brought into an excessively high pressure state, a stable air pressure cannot be supplied to the ink cartridge. Further, when inside of the air supply tube space stays in the high pressure state in interchanging the ink cartridge, also a space in the cartridge communicated with the tube is brought into a high pressure state and the ink cartridge is brought into an expanded state and therefore, the ink cartridge becomes difficult to remove.
Therefore, it is necessary to arrange a pressure releasing mechanism for releasing pressurized air in the tube to outside. As the pressure releasing mechanism, there is known a pressure control valve serving also as an atmospheric release valve shown in, for example, JP-A-2001-212975 (pages 8 through 9, FIG. 7). The pressure control valve is constituted by a valve opening/closing structure using an electromagnetic valve, in details, a structure of bringing about a valve opening state by moving a lever or the like when electricity is conducted to an electromagnetic plunger by an instruction from a control apparatus. Further, inside of the air supply tube is released to the atmosphere by opening the pressure control valve when the air supply tube is brought into the excessively high pressure state or when a power source of the printing apparatus is made OFF.
In this case, there is conceivable a constitution of combining, for example, JP-A-2000-352379 and JP-A-2001-212975 as a printing apparatus of an off-carriage type having a pressure control valve (serving also as an atmospheric release valve). However, when the diaphragm type pump shown in JP-A-2000-35237 is used, in view of a current situation that since a plurality of pump chambers are present on the same plane of the pump, a diameter of the pressurizing pump is large, there poses a problem that the pressurizing pump and therefore, the printing apparatus is large-sized.
Further, the pressure control valve shown in JP-A-2001-212975 is constituted by the structure of using the electromagnetic valve having a large size, also in the case of using the pressure control valve, there poses a problem that a pump unit including the pressurizing pump and the pressure control valve and therefore, the printing apparatus is large-sized. Further, when the pressure control valve shown in JP-A-2001-212975 is used, in addition to control of the drive motor for moving the pressurizing pump, also a control of the pressure control valve is needed to thereby pose also a problem of complicating a control system.
Further as the pressurizing pump disclosed in JP-A-2000-352379 (pages 4, 5, FIG. 1), a printing apparatus is mounted with a pressure detector for detecting a pressure of pressurizing air discharged by a pressurizing pump and a control apparatus for calculating a pressure value of pressurizing air based on a detected value of the pressure detector. Further, when the pressure value of the pressurizing air is lower than a set pressure, the pressurizing pump is brought into a driving state, when the pressure value of pressuring air is not less than the set value, the pressurizing pump is brought into a stationary state and pressurizing air is maintained at a pressure value in a predetermined range by repeating to drive and stop the pressurizing pump.
Meanwhile, when a pressure waveform 90 of pressurizing air is shown in FIG. 23, a pressure of pressurizing air drops with an elapse of time after stopping driving the pump by being caused by a small amount of leakage of an air path, an increase in a space volume in an ink cartridge by consuming ink or the like. Therefore, when the pump is stopped to drive immediately at a time point at which the pressure value of pressurizing air becomes a set value, it is necessary to restart to drive the pump by a short time interval and therefore, a frequency of stopping and restarting to drive the pump is increased and a hindrance is brought about in durability of the pump. Hence, as shown by a one-dotted chain line of FIG. 23, the problem is dealt with by applying additional pressurization by continuing to drive the pump for a predetermined time period even when the pressure value becomes not less than the set value and stopping driving the pump after making the pressure value of pressurizing air higher than the set value.
Here, depending on cases, there also is a case in which the pressure value of pressurizing air becomes not less than the set value in a state in which the diaphragm is contracted and the pressurizing pump is stopped in the state in which the diaphragm is contracted. In this case, the diaphragm is left for a long period of time in the contract state and there is also a possibility of deforming the diaphragm by creep thereby. When the diaphragm is deformed by creep, there is brought about a state in which the pressurizing pump cannot exert a sufficient pressurizing force and therefore, there poses a problem of deteriorating a pumping function of the pressurizing pump.